package TRANVIETHOANG;

import java.util.Scanner;


	public class HOMEWORK_02 {

		public static void main(String[] args) {

			// Input a,b
			String a, b, pheptoan;

			Scanner in = new Scanner(System.in);

			// Read input, check null

			do {
				System.out.println("Nhap a = ");
				a = in.nextLine();
				System.out.println("Nhap b = ");
				b = in.nextLine();

				if (a.isEmpty() && b.isEmpty()) {
					System.out.println("Ban chua nhap so");
				}

			} while (a.isEmpty() || b.isEmpty());

			double m = Double.parseDouble(a.trim());
			double n = Double.parseDouble(b.trim());

			do {
				System.out.println("Xin hay chon phep toan (cong/tru/nhan/chia): ");
				pheptoan = in.nextLine();

				if (pheptoan.isEmpty()) {
					System.out.println("Ban chua cho phep toan.");
				}
				

			} while (pheptoan.isEmpty());

			if (pheptoan.contentEquals("cong")) {
				System.out.println("Ket qua la " + (m + n));

			} 
			
			else if (pheptoan.contentEquals("tru")) {
				System.out.println("Ket qua la " + (m - n));
			}

			else if (pheptoan.contentEquals("nhan")) {
				System.out.println("Ket qua la " + (m * n));
			}

			else if (pheptoan.contentEquals("chia")) {
				if (m == 0 && n == 0) {
					System.out.println("Result of function is undefined");
				} else if (n == 0) {
					System.out.println("Cannot divided by zero");
				} else {
					System.out.println("Ket qua la " + (m / n));
				}

			}
		}
	}
